The present invention relates to a method and an apparatus for manufacturing electronic circuit boards, and particularly to a multi-layer board manufacturing method and a multi-layer board manufacturing apparatus suitable for manufacturing multi-layer ceramic boards.
Recently, the mounting configuration of electronic circuit components such as ICs and LSIs, which are used not only in information equipment but also in household appliances and automobile parts, has become denser. With the increasing density of mounting configuration, there has been a stronger tendency to increase the density and layers of electronic circuit boards for mounting electronic circuit components. Ceramic boards, which are laminated with green sheets and sintered, are becoming dominant as a material for electronic circuit boards.
When a ceramic board is manufactured, through holes are formed in green sheets, and circuits are formed by printing. After laminated and bonded by pressing, the green sheets are cut to board size, and then sintered to form a ceramic board. In methods for manufacturing ceramic boards, cutting is performed by methods using cutter blades or stamping methods using dies, as disclosed, for example, in Japanese Patent Laid-Open No. Hei 5-190374, Japanese Patent Laid-Open No. Hei 9-104018, Japanese Patent Laid Open No. Hei 10-335170, and Japanese Patent Laid-Open No. Hei 11-90894. The methods mentioned above are for mechanical processing.
On the other hand, as disclosed in, for example, Japanese Patent Laid-Open No. Hei 9-1369, there is a known method in which a board is laminated with green sheets and sintered, and then the sintered multi-layer board is cleaved by using a laser. A laser cleavage cut is performed by irradiating the surface of the multi-layer board with laser light with a large beam diameter at a position off the focal point, so that thermal stress occurring in the heated part due to the laser light causes the multi-layer board to be cleaved.
In methods of cutting a multi-layer ceramic board by mechanical processing, the number of electronic circuit boards manufactured from a green sheet is limited, and therefore it presents a problem of low yields. In order to increase the yields, electronic circuit boards with a plurality of sizes may be arranged on a large green sheet in such a way as to eliminate waste. With mechanical processing methods, it is impossible to cut the plurality of circuit boards arranged close to each other on the green sheet. The reasons for this include a large cut margin resulting from a mechanical processing method and the incapability of mechanical processing methods to perform two-dimensional cutting. Two-dimensional cutting will be described later in detail. One-dimensional cutting means that a sheet is first cut sequentially only in one direction, and then the cut long, narrow sheet is further cut in a direction perpendicular to the above cutting direction. On the other hand, two-dimensional cutting means that after a electronic circuit board is cut along a first side of the electronic circuit board, the cutting is continued along a second side of the electronic circuit board which is perpendicular to the first side.
In the method of cleaving a sintered multi-layer board by laser light, irregularities are formed on the cut surfaces, which can cause a crack and therefore present a problem of a low yield.
The present invention provides a method and an apparatus for manufacturing multi-layer boards, which will improve yields in the manufacturing of electronic circuit boards.
A manufacturing method according to the present invention comprises the steps of:
preparing a plurality of green sheets;
forming at least one board pattern on each of the plurality of sheets;
laminating and bonding each of the plurality of sheets to form a multi-layer board; and
cutting the multi-layer board by irradiating the periphery of at least one board pattern on the surface of the multi-layer board with laser light.
Thus a section in the multi-layer board where at least one board pattern is formed is cut away from the other section of the multi-layer board. The section of the multi-layer board cut away from the other section of the multi-layer board is sintered. As a result, a multi-layer board is produced.
The unsintered multi-layer board is cut by heating and melting with laser light. This makes it possible to improve the yield in the manufacturing of electronic circuit boards.
A manufacturing apparatus according to the present invention has a stage for mounting a board. The stage moves a board in the directions of two axes which are in parallel with the board and perpendicular to each other. A laser optical unit is placed above the stage to irradiate the board mounted on the stage with laser light and cut it. The width of the cut portion in the board created by laser light is measured by a width measuring unit. A stage controller, which controls the movement of the stage, controls the velocity at which the stage moves, according to the width measured by the width measuring unit.
The kerf width can be made almost constant and narrow, by monitoring the kerf width and controlling the cutting velocity by using feedback.